In various types of industry, several bagged products are composed of a mixture of 2 or more products. This is the case, among others, of certain animal foods, potting mixes, concrete mixtures, etc. In the cited examples, the importance of the homogeneity of the mixture and the proportions or quantities of each product is relatively low (usually not regulated or standardized). In some other cases, there is a need to homogeneously mix two products (or more) while ensuring that one of the products can be precisely measured to guarantee a minimum proportion or quantity of the latter in a precise quantity of the final blend. The seed industry is a prime example of this type of need.
In the seed industry (corn for example), the growing presence of genetically modified organisms (GMO) or genetically modified seeds (GM seeds) (referred to below as a main product) has created the need to implement laws to control environmental integrity. An example of genetic modification was to create a seed containing (into its genome) a common gene known to be toxic to several varieties of predators' larvae. In doing so, the plants themselves were able to produce a toxic protein and thus become resistant to predators (such as insects) without the need for spraying pesticides. To prevent environmental problems (such as insect mutations or insect dissemination), environmental authorities (such as the Environmental Protection Agency, EPA) established regulations concerning the use of these GM seeds. According to these regulations, the farmers were enforced to use a minimum percentage (traditionally 20%) of non-GM seeds, also known as “refuge” or sacrificial seeds (referred to below as an auxiliary product). This practice is intended to prevent the development of organisms resistant to the GM seeds or ensuring that enough organisms not in contact with GM seeds survive to reproduce. At that time, seed producers realized the competitive edge they would get if they succeed in reducing the proportion of regulated refuge seeds. In fact, non-GM seeds are more vulnerable and more likely to generate losses since they are not treated against predators. Consequently, reducing their proportion will reduce the farmers' losses. Advances in this field allow a decrease of the proportion of non-GM seeds (in such cases 5%). The EPA accepted this reduction but regulated that farmers were no longer allowed to make the compliant refuge proportion (blend) themselves. Seed producers were appointed to make the blend, to record production data and to regularly report to the EPA. Then, they started developing (among others) the concept of refuge-in-the-bag (RIB) which provides the right blend (both type of GM and non-GM seeds) based on the refuge percentage required for a particular corn technology. The RIB concept is convenient for farmers because it enables them to plant only one seed product and brings the following benefits: easier planter configuration, less losses, lower operating costs, less manipulation, less proportion errors, more homogeneous fields, etc. . . . ).
In this example, it is understood that there is a product in a first proportion (which is referred to below as the main product) in which will be incorporated added product(s) of a second proportion (referred to below as the auxiliary product).
Weighing equipment used in the bagging process of products that need to be weighed, such as industrial scales, are equipped with a weighing controller that measures the correct weight to be put into each container.
In the present description, it is to be understood that the term “dosing” includes actions of carrying out a measurement (such as weighing, for example) of a product and releasing the product.
The main characteristics required for dosing and blending seeds are summarily presented hereinbelow:                The system should precisely measure the auxiliary product (in this case by weight) to meet regulatory requirements, such as from the EPA, and the total quantity of the blend (auxiliary product and main product), and record these values to meet economic and market requirements. In order to obtain a precise total weight, the system may vary the main product quantity according to the (previously measured) auxiliary product.        The proportion of each product in a specific unit should be precisely controlled and may be flexible (it is possible to vary the proportion of each product) in order to meet standards or legal requirements.        The system should provide a homogeneous blend (evenly distributed) since it is governed by the laws. Moreover, provision of a homogeneous blend allows the use of a portion of a unit (a bag for example) knowing that homogeneity is respected throughout the whole unit.        The system should record and track the measured auxiliary product as well as record and track the total blend quantity and product proportions of each unit. These data may be compiled to allow the issuance of reports to legal entities if required.        The system should be compact to be integrated to typical packaging systems, and can be retrofitted to existing packaging systems.        The system provides increased productivity at a lower cost.        
The prior art documents teach that some dosing and blending systems dedicated to dose different products possess some of the characteristics described hereinabove, but none of them adequately meet all of the described requirements. The following summary analysis highlights the weaknesses of the existing dosing and blending systems.
“Mixing before weighing” processes use different means to mix the products before the dosing operation and measure the total product weight. These systems cannot guarantee the proportions of the blend or homogeneity of the blend due to probable segregation happening in the systems between the mixing action and the final weighing. Therefore, “mixing before weighing” is not an adequate solution in contexts and applications where requirements are more strict.
Combination scales (also named multi head weighers) include several weigh pans (up to 24) which perform accurate weighings of one or multiple products, allowing proportion control, recordability and traceability of data. A certain number of these weighings are combined to reach (or to get as close as possible to) the desired weight, which is calculated. However, combination scales cannot guarantee the homogeneity of the blend since they drop the different products together in a filling chute and rely on the falling action to mix the blend. Moreover, for most of the existing packaging plants, these weighers are too large to retrofit the weighing systems already in place.
Dedicated dosing systems (as described in U.S. Pat. No. 7,137,729 B2) can provide a homogeneous blend using a mechanical blender. However, this practice lengthens the system cycle time (thus reducing production rate) and takes up too much place to be integrated with typical compact bagging systems. These systems measure the total product weight, but cannot guarantee the product proportions.
The following table illustrates how the above-mentioned prior art teachings address in part the above needs:
Prior artMixing beforeCombinationU.S. Pat. No.Characteristicsweighingscales7,137,729Measure auxiliary———product/Measure blendProportion controlled—√—and flexibleHomogeneous blend—√Record and Track√√√Compact system—Production rates/cost———Legend:√ Complete solution— Partial solution  No solution
Although different dosing systems are already known and satisfy at least one of the above needs, there is still a need for a dosing system which will meet a majority, if not all, of the requirements described above.